This invention relates to a press brake with improved ram leveling adjustment and more particularly to a press brake having hydraulic-mechanical power means for advancing and returning a ram and separate leveling means for independently adjusting the level of each end of the ram.
The correct angular adjustment or level of the moving ram of a press brake is important in precision work such as in the bending of heavy sheet and bar metals. The size and weight of a press brake increases with the thickness of the metal which the press brake is designed to bend and machines of three hundred tons or greater are not uncommon. Efficient production requires that the press brake, even though of great size and weight, be capable of rapid adjustments inorder to reduce set-up time of the machine to a minimum.
Press brakes having hydraulic mechanical power means for advancing and returning a ram relative to a stationary bed are disclosed in the prior art, as for example in U.S. Pat. No. 3,763,690 issued Oct. 9, 1973 to Joseph A. Kirincic and Raymond J. Heitner, and assigned to Dreis and Krump Manufacturing Co. The press brake disclosed in the aforesaid patent has leveling adjustment means for the ram which includes substantially parallel, linked bell cranks, each having a pivot at the fulcrum thereof by which the bell crank is pivotally supported to the frame of the press brake and at least one of the bell cranks having a pivot which includes an eccentric pivot pin which can be rotated to a desired position for ram leveling adjustment. The eccentric is rotated by means of a worm gear which is driven by a manually actuated crank.
It is further known in the prior art to adjust the position of the ram of a press brake with respect to a bed by simultaneously varying the length of a pair of pitmen which support opposite sides of the ram from mechanical operating mechanism. U.S. Pat. No. 2,237,170 issued Apr. 1, 1941 to Larkin R. Williamson and assigned to E. W. Bliss Company discloses a machine having the aforesaid capability. The adjusting means comprises an electric motor which drives a telescoping shaft extending across the ram and connected at each end into the pitman construction at the ends of the ram. A pair of worms are carried at the ends of the shaft and each engages respectively with a worm wheel keyed to each lower pitman element. Each of the pitmen comprises a lower pitman element swiveled in a socket at one end of the ram and an upper pitman element comprising an internally threaded sleeve, one end of which is pivotally connected to an eccentric for raising and lowering the press brake ram. Thus depending on the direction in which the motor driven shaft rotates the lower pitman elements at each end of the ram, the pitmen will be shortened or lengthened, and the ram is raised or lowered with regard to the upper pitman structure to adjust the ram with respect to the stationary bed.